1. Field of the Invention
The present invention relates to equipment for the manufacture of optical fiber couplers used in communication systems and for optical sensors, etc., and in particular, relates to equipment for the manufacture of fused-elongated type optical fiber couplers.
2. Prior Art
Optical fiber couplers formed from a fused-elongated region are well known in the art, and conventional methods for their manufacture have been described, for example as is shown in FIGS. 9 to 12. Referring to these drawings, first of all as shown in FIG. 9, a portion of two component optical fibers 1 from which the protective coating has been removed thereby exposing the clad 2 are aligned in contact side by side and fixed in this configuration using an adhesive agent. Next, the thus joined sections of exposed clad 2 of the component optical fibers are fused by heating with an oxygen-hydrogen flame 3 or similar high temperature heating apparatus, and the fused section is then drawn out, thereby forming the fused-elongated region 4 as is shown in FIG. 10.
With the kind of optical fiber coupler formed as described above, ordinarily the fused-elongated region 4 is fixed to a reinforcing plate 5 made of metal, glass, or the like using an adhesive agent 6, as shown in FIG. 11. Finally, the optical fiber coupler and the plate to which it is attached is usually placed in and covered by a section of metal pipe as shown in FIG. 12, whereby the coupler is mechanically reinforced and protected.
For the above described drawing out of the fused section of component optical fibers 1, as shown in FIG. 13, a pair of extender stands 8 may be used, the linear movement of which can be effected and controlled using respective screw mechanisms. During the manufacture of this type of fused-elongated type optical fiber coupler, it is essential that the extent of elongation be accurately controlled during the drawing out process. For this reason, a light source 10a is provided at one end of one of the component optical fibers 1, while light power meters 10b, 10c or similar devices for measuring light intensity are provided at the opposite end of both component optical fibers 1 as shown in FIG. 14, whereby the coupling ratio for the fused-elongated region 4 under formation can be determined while the fused region is drawn out, thus permitting highly accurate control of the coupling ratio of the optical fiber coupler that is produced.
However, with the above described conventional manufacturing method for fused-elongated type optical fiber couplers, the following problems exist:
1. In the method as described, separate left and right extender stands were employed, the movement of which is independent of one another. For this reason, it is very difficult to manufacture a fused-elongated type optical fiber coupler having symmetrically formed right and left halves. PA0 2. The manufacturing method described above requires two or more individual devices and is thus prone to be cumbersome. Further, the various devices required are likely to occupy a relatively large work space. PA0 3. Furthermore, by employing a separate light source and light power meters in addition to the left and right extender stands, not only are the problems described in 2 above aggravated but further, it is often the case that additional length is required for the component optical fibers extending from the optical fiber coupler to the light source and light power meters.